This invention relates to signature gathering machines in which successive signatures are fed to and collected into a book on a conveyor.
Books, including magazines, are composed of signatures which are simply folded sheets bearing the printed matter. The signature may present pages of the usual kind, or it may be a special size insert. The individual signatures which compose the book are fed from corresponding hoppers or so-called pockets and the signatures for each book are eventually collected one atop another, or one aside another as the case may be, on a conveyor and are transported by the conveyor to a station in the machine where the signatures are joined into a book by stitching with staples or by gluing, depending on how the book is bound.
A signature gathering machine for composing a magazine may have up to thirty or more hoppers. This is especially so in the instance where various inserts are to be included at the proper place among the signatures in the course of gathering the signatures into a book.
It is now common for magazine editions to be subjected to so-called demographic controls. This is explained as follows. For the most part, signature gathering machines operate on the principle of zone mailing. For example, the signatures may be gathered on the basis of the entire mailing to a particular city, and such mailing will include the news stands, residential subscribers, institutional subscribers and so on in that particular zone. The books emitting from the machine are usually in alphabetical order for a particular zone. However, some publishers may require that there be so-called demographic separation of subscribers in terms of professional groups, student editions, and so on, regardless of zone. Demographic separation may be founded on such differences as subject matter content, advertisements, inserts and so on.
Production of these various editions complicates the signature machine in several respects. For example, the pocket feeders must be controlled to feed the proper signatures for the various editions. This aspect is discussed in McCain, U.S. Pat. Nos. 3,608,893 and 3,774,901.
Another problem with demographic editions is the books presented to the binding machine have variable thicknesses. Therefore, the binding machine must be capable of handling the variable book thicknesses. If, for example, the books are being stitched, the stitcher heads must apply proper compression to the saddle of the books. If there is too much compression, there will be a bulge in the back bone of the stitched book while if there is too little compression, the staple will be loose.
Conventionally, the stitcher heads are pre-set to accept one particular book thickness, the movable parts of the stitcher head descending the correct distance to properly engage a book of given thickness. But since the demographic editions will have variable thicknesses, fixed stitcher heads are subject to the errors mentioned above.
One approach to this problem is disclosed in U.S. Pat. No. 3,899,165. There the stitcher drive mechanism is adjusted for every book. In other words, the thickness of a book is determined and the stroke length of the stitcher head parts is adjusted accordingly so that each staple is properly formed. This technique does not lend itself to high speed production (on the order of five books per second). There is simply too much hardware to move accurately in the time available. Also, this method produces staples of improper length. This is because the stitcher head drive mechanism also controls the wire cutters that determine staple size. Since the wire is cut several book cycles in advance of driving it as a staple, adjustments made after cutting the wire will mean the wire is the wrong length for the newlychanged drive stroke.
Known stitcher heads are employed in the binding machine of the present invention. For example, Bostitch model 18001 stitcher heads may be used. These heads are supplied with wire from a spool. The length of wire from which the staple is formed is cut and positioned vertically in a groove of a swivel which is then turned to dispose the wire length in a horizontal position. Afterwards a bender bar shapes the wire to a U-form while the wire is held by the swivel. Next, a driver bar carries a related driver downwardly. The free end of the driver engages the swivel and causes it to be retracted. As the swivel is retracted, it releases the bent wire to a pivotal support member; the legs of the bent wire are supported by grooves in the bender bar. The driver and support member cooperate to square off the crown of the staple. Further descent of the driver bar and driver is characterized by the end of the driver engaging the support member to move the latter to a retracted position and at the same time the driver forces the wire into the book. The legs of the staple are clinched by fingers on the underside of the book.